I had two starts, really. The first was going to the Italia Conti stage school, aged 15. I'd gone to sing, but one day I found myself doing an improvisation and thought, "Oh God, I quite like this acting thing." The second start was meeting Mike Leigh when I was 22. He showed me I could play people that weren't like me. It was like a lightbulb going off.

What was your big breakthrough?

Making a film called Grown Ups with Mike Leigh in 1980. Both of the pieces we'd worked on together before that hadn't actually come to anything. First tThere was a radio play, Too Much of a Good Thing, about a girl losing her virginity, which got banned initially by the BBC for its realistic-sounding sex scenes. Then And there was a play we did for the RSC that never saw the light of day. But Grown Ups opened doors for me in a major way – I spent the next 10 years working at the Royal Court.

Do you suffer for your art?

Not any more. But I did when my son was young and I was a single mother. A lot of the actors I knew threw in the towel when they became mothers. I couldn't do that financially, and I didn't want to – but I was knackered all the time.

What's the biggest myth about being an actor?

People mistake the fact that we have a nice time at work for it being easy. I spent last week in the dark, freezing, doing hellishly long days. Then there's the fact that people think you're always earning a fortune. That's absolutely not the case – especially in subsidised theatre. Actors often have to turn down a play because they can't afford it, unless they can do a bit of telly either side.

Stage or screen?

Stage is the ultimate test; I like watching established screen actors on stage to see if they can really do it. But it's great to have a healthy mixture of the two. Film is so technical: there's something very particular about the relationship between you and the camera. It took a long time for me to get good on film.

What work of art would you most like to own?

I'm a big fan of Edouard Vuillard, so I'd like anything by him – particularly a painting called Madame Hessel on the Sofa. His work is realistic without being literal: I can really imagine what Madame Hessel is thinking.

Is there an art form you don't relate to?

I have trouble with sheep in formaldehyde.

What's the worst thing anyone ever said about you?

A director once said to me, "I've got no notes for you, except act better."

Do you care about fame?

No. I'd hate not to be able to travel on the tube. I quite like that people tend not to know my name. I remember being at the Cannes film festival for All or Nothing. I looked very different in the film – I had a little greasy bob and no makeup. I went to a dinner after the screening and everyone completely ignored me. I got a real buzz out of that.

In short

Born: Brighton, 1956.

Career: Has worked frequently with Mike Leigh, in his films – including High Hopes, Secrets & Lies and Another Year – and his stageplays. Has also performed at the Royal Court, with the RSC and at the National Theatre; and, most recently, in the BBC TV series Mayday, which is out now on DVD.